The invention relates generally to a transfer switch, and more particularly to system for reverting to an alternative electric source during a power failure.
The reliable supply of electricity is important for businesses and homes. Indeed, virtually every business and home relies upon the continuous supply of electricity to refrigerate food, to operate heating and cooling systems and many other appliances.
In some applications, the uninterrupted supply of electricity is absolutely critical. For example, computer systems generally require a virtually perfect power supply. Even a momentary glitch can disrupt their operation. Consequently, where the supply of electricity is unreliable, back-up power sources commonly referred to uninterrupted power supplies are used. These usually include a power detection and filtering circuit. If the main power fails, the back-up power source immediately detects the failure and switches to a battery or other back-up source. In more sophisticated systems, the back-up power source will switch to an alternative power supply such as a generator if the main power remains off line.
Although these types of systems are effective even for the most demanding of applications, they are also expensive. The circuitry required to monitor the main power supply and associated battery back up are relatively complex. Moreover, this type of uninterrupted power supply is not necessary for many applications. For example, many businesses or homes can tolerate a short interruption in their power supply. Interruptions of only a few minutes have little affect on heating or cooling systems. Critical applications such as a computer can depend upon a local back-up power supply. If the main power supply continues to fail, a local generator can be started to provide backup power.
The installation of a back-up generator requires that it is connected into the loading circuits in a manner that does not interfere with the normal delivery of power from a local utility company. The back-up generator must be disconnected when the local utility company provides power to prevent large flows of electricity between the two sources. In most conventional home or business settings, the internal wiring is connected directly to the local utility company through a power meter and breaker switches. The power meter is used to monitor usage for billing purposes. The breaker switches are used to prevent excessive flow of current through any loading circuit.
The addition of an auxiliary generator to a conventional home or business requires significant changes to the internal wiring, and typically requires the addition of an auxiliary cabinet. This cabinet houses switches and the additional wiring required to accommodate the generator.
For an existing structure, the installation of an additional cabinet and associated wiring requires significant modifications. The cabinet must be mounted and, depending upon the installation, generally cannot be mounted flush with the surface of the wall. In addition, external conduit generally is required to house the additional wiring. These external additions are cumbersome at best. Accordingly, an improved method of installing an auxiliary generator is desired.
According to one preferred aspect of the invention, a transfer switch system is especially suited for connecting loading circuits to a normal power source and to an emergency power source. The transfer switch system includes an enclosure, an electrical power meter, a normal power switch, an emergency power switch, and a handle. The enclosure has a front face and a plurality of side walls. The front face of the enclosure defines a circular hole sized to fit an electrical power meter. The side walls of the enclosure define holes for passing wires that carry electrical power from a normal power source and an emergency power source and at least one hole for passing wires that carry electrical power to loading circuits. The electrical power meter is mounted within the enclosure and extends through the circular hole in the front face. The electrical power meter is electrically connected with the normal power source to measure the electrical power flowing from the normal power source. The normal power switch is mounted within the enclosure and electrically connected to the normal power source and to the loading circuits. The normal power switch is configured to connect the normal power source to the loading circuits in an on position and to disconnect the normal power source from the loading circuits in an off position. The emergency power switch also is mounted within the enclosure proximate the normal power switch. The emergency power switch is electrically connected to the emergency power source and the loading circuits and configured to connect the emergency power source to the loading circuits in an on position and to disconnect the emergency power source from the loading circuits in an off position. The handle is mounted on the front face of the enclosure proximate the normal power switch and the emergency power switch. The handle includes a bracket extending into the interior of the enclosure to engage the normal power switch and the emergency power switch. Operation of the handle to a normal position places the normal power switch in the on position and the emergency power switch in the off position; operation of the handle to the emergency position places the normal power switch in the off position and the emergency power switch in the on position.
According to another aspect of the invention, a power meter and switch box are especially suitable for selecting between a utility power supply and an auxiliary power supply. The combination includes an enclosure, a meter, an auxiliary power terminal, a breaker switch, a set of power switches, and a handle. The enclosure has a first chamber and a second chamber. The meter is electrically connected with a utility power supply and configured to determine the amount of electrical power that has been used from the utility power supply. The meter is mounted within the first chamber of the enclosure. The meter includes a display that extends through a hole defined by the enclosure so that the amount of electrical power that has been used from the utility power supply can be readily determined. The auxiliary power terminal is configured to removeably connect with an auxiliary power supply. The auxiliary power terminal is mounted within the second chamber of the enclosure. The breaker switch is configured to removeably connect with a loading circuit. The breaker switch is mounted within the second chamber of the enclosure. The set of power switches is connected between the meter and the breaker switch and between the auxiliary power terminal and the breaker switch and are configured to operate in tandem. When the set of power switches forms an electrical connection between the meter and the breaker switch, the electrical power switches disconnect the auxiliary power terminal from the breaker switch. Likewise, when the set of power switches forms an electrical connection between the auxiliary power terminal and the breaker switch, the electrical power switches disconnect the meter from the breaker switch. The set of power switches are mounted in the second chamber. The handle engages the set of power switches and has a normal and an auxiliary position. Operation of the handle to the normal position causes the set of power switches to form an electrical connection between the meter and the breaker switch. Operation of the handle to the auxiliary position causes the set of power switches to form an electrical connection between the auxiliary power terminal and the breaker switch.
According to a further aspect of the invention, the handle includes a bracket that extends into the enclosure and engages the set of switches. The bracket includes a first and a second u-shaped plate and a flat plate. The first u-shaped plate defining a pair of slots. The flat plate extends through the pair of slots in the first u-shaped plate so that the flat plate is free to move along a first axis but is restricted from moving in any other direction by the confines of the pair of slots. Movement of the handle moves the flat plate along the first axis. The second u-shaped plate extends from the flat plate and is positioned so that the set of switches are confined between the walls of the u-shaped plate. Thus movement of the flat plate causes the u-shaped plate to operate the set of switches.